1. Field of the Invention
This invention relates to the flotation barrier or boom art, and, more particularly, to an improved contamination containment barrier or boom.
2. Description of the Prior Art
The increased frequency of contamination of bodies of water such as rivers, harbors, lakes, oceans, and the like, by, for example, oil spills, has increased the need for effective containment barriers or booms wherein the area of the liquid body having the contamination may be separated from adjacent areas of the liquid body and the contamination contained within the sectioned off area. The contamination may be removed without further contamination of additional areas.
Various types of booms have heretofore been utilized for providing the barrier separating the contamination area from uncontaminated areas. One type of boom that has been widely utilized is a flotation boom, generally fabricated in sections. Each section of the boom may be coupled to adjacent sections to form an entire boom of any desired length deployed in any desired geometrical configuration to contain the contamination area. Such flotation booms have generally incorporated a flotation means floating on the surface of the liquid and a depending weighted skirt extending from the bottom of the flotation means into the liquid. The skirt has a predetermined depth and generally incorporates a ballast, and preferably a tension member. A towing nose and/or towing tail is usually attached to the end sections of the assembled boom providing a strong and convenient means of coupling the boom to a towing vessel or ship.
The older forms of flotation means heretofore utilized have comprised, for example, logs, sealed rigid containers such as empty drums, inflatable tubular members, tubular members filled with a buoyant material, i.e., a material having a specific gravity less than 1.0, or similar devices. However, such older prior art flotation means arranged as a containment boom have generally not proven to be completely satisfactory.
Since the containment boom is often stored comparatively long periods of time and only deployed on the liquid when it is necessary for training or to contain a contaminated area, the storage volume should preferably be as small as possible. Also, since boom performance is a function of flotation volume, storage volume tends to be very large. Further, since the contamination may occur quite suddenly, the boom should be able to be rapidly deployed with comparatively low drag and low turbulence inducement in the liquid. Further, it should be deployable without utilizing sophisticated machinery and/or highly skilled labor.
Additionally, it is also desired that the boom be capable of articulation in both the horizontal and vertical directions, while generally maintaining its cross-sectional configuration, in response to the forces imposed by winds, waves, and the like. A boom of such design minimizes stress imposed on the boom, maintains desired draft and freeboard, and minimizes splash-over. Further, each boom section is preferably fabricated in as longitudinally long sections as possible to avoid complications on deployment or when used, and to reduce costs associated with boom section connections.
Inflatable booms enable relatively small storage volumes to present relatively large flotation when deployed. One form of inflatable boom heretofore utilized has incorporated a plurality of boom sections, each approximately 25 yards long and has a flotation portion and a depending skirt portion. The flotation portion is of flexible fabric and has a generally rectangular configuration in the deployed condition and is transversely collapsible in the stored condition to a flat configuration in which it may, for example, be coiled. Each section is comprised of a plurality of elements on the order of 1 to 2 yards long. Each element has one or more individual spring loaded, pivotally connected, rectangular frames and a check valve for admitting air into the section. In the collapsed, or storage condition, the springs allow the collapse of the rectangular frames to permit the boom to assume the transversely flat storage configuration. Means are provided, in the storage configuration, to resist the spring forces and prevent opening of the boom. On deployment, the restraints are removed and the springs force the rectangular frames into the rectangular configuration, sucking aire into the tubular member through the check valve, and the trapped air in the boom provides buoyancy. The trapped air in the boom exceeds atmospheric pressure to resist the natural liquid forces acting thereon which tend to transversely collapse the boom and, thus, the combination of the trapped air and the spring loaded frames are required to maintain the structural integrity and buoyancy of the arrangement. On retrieval of the boom section, air must be vented by manual operation of the valves, and each rectangular frame must be collapsed and means provided to retain the collapsed configuration. Such operating mechanical structures in the interior of the boom, the automatic opening as well as the labor associated with retrieval, the leaking of liquid into the individual elements, the difficulty of removal of water and sinking of the boom, have made such boom elements unsatisfactory in may applications. Such a boom is described, for example, in U.S. Pat. No. 3,798,911.
Yet another type of boom is described in U.S. Pat. No. 3,576,108, but such structure as shown therein does not readily lend itself to a comparatively small volume for transport or storage.
Another type of boom is described in U.S. Pat. No. 3,686,869, in which a plurality of float chambers are connected to a dependent skirt portion extending below the surface of the body of liquid, and in each float chamber therein is provided a spring. While the boom of U.S. Pat. No. 3,686,869 may, under some circumstances be wound on a reel for storage, and then deployment therefrom, the springs in the storage condition are axially compressed against the spring constant. Further, the flotation chambers of the structure shown in U.S. Pat. No. 3,686,869 extend substantially perpendicular to the elongated longitudinal direction of the dependent skirt portion, thus adding considerable bulk, mass, and cost to another form of such a configuration.
U.S. Pat. No. 3,811,285 shows another form of boom arrangement, in which a plurality of flotation pockets, open at the bottom, are vertically arranged in spaced relationship throughout the longitudinally elongated boom section. Within the flotation pockets, there may be provided helical springs which have a plurality of straps coupling the coils of the spring to the vertically oriented pockets on the interior thereof. Thus, the axes of the helical springs are vertically oriented. While this configuration may be wound upon a reel for a storage condition, it has been found that collapsing the helical springs during the winding, because of their vertical orientation as opposed to the elongated longitudinal dimension of the boom section, presents considerable problems, since forces are not acting directly upon the spring to cause the collapse thereof into a flattened condition. That is, in winding the structure shown in U.S. Pat. No. 3,811,285 upon a reel, the forces act in a direction perpendicular to the axis of the helical coils and some additional force must be provided on the helical coils, acting in the axial direction to cause the coils to collapse to a flattened condition.
U.S. Pat. No. 4,068,478 discloses structure in which a helical member extends throughout the longitudinal direction of a tubular member, forming the flotation chamber of a containment boom section, and which is adapted to be longitudinally compressed during the storage thereof.
U.S. Pat. Nos. 3,803,848 and 4,295,755 disclose yet other configurations of a containment barrier or boom.
In my earlier PCT Application Number PCT/US80/01488, International Publication No. WO 81/03198, a self-inflating, collapsable containment barrier or boom is shown and described in which a continuous coil of spring-like material is resiliently deformable from a helical condition to a transversely flattened condition. Upon deployment, the coil reverts back to its helical condition, thereby expanding the tubular cover. While this arrangement has proven to be a functionally attractive and useful arrangement, manufacturing, handling, and installing a long spring coil is difficult and expensive. In this prior invention, a flexible flotation member is provided in the form of a thin flexible wrap surrounding the inner structure of the flotation tubular member.
Another prior art contamination control boom which uses a helical wire interior structure and float means is shown and described in my prior U.S. Pat. No. 4,752,393 issued Jun. 21, 1988. While this patent shows an internal foam strip, it is held in place by an attachment means structure which requires assembly and adds to the complexity and cost of the arrangement.
It has been found that a boom, which may be windable upon a reel during the storage thereof, and have reduced volume when so wound on the reel, but automatically expand to its desired volume upon deployment or unwinding from the reel, and which is constructed to include enough foam flotation to assure buoyancy even if inflated chambers are full, offers many advantages in certain applications. To achieve such automatic expansion to a full flotation condition upon deployment, it is preferred that the mechanism providing such expansion be substantially free of comparatively complex mechanical elements, and, further, that the structure should collapse automatically, during the winding upon the reel, without utilization of any other forces to cause the collapse of the structure. Additionally, of course, the boom section should expand into its full flotation volume upon deployment from the reel, and, once again, such expansion should also be achieved without the requirement of applying any other forces except the unwinding from the reel to achieve such an expanded condition.